RR,
During a Boeing approach, you try to maintain a constant speed by changing power. You oscillate around this speed, generally your trim is constant as you return to datums after any disturbance.
During an Airbus approach with GsMini active, your datum speed can change by 40 knots. As such, your power, speed hence trim will change, requiring you to retrim during the whole approach, which is challenging when you also have to adjust power. Hence what Airbus recommends is going to Conf3, getting speed stable, allow the aircraft to sort the trim, then Gear down.
Anyhow, say this did happen and you flew an approach which had a incident. The authorities are going to look at the way you flew that approach against the SOP's, bearing in mind the FCTM quotes you MUST use selected. If you think managed is a good idea, why not put it to Airbus?